Zirabev is neither traditional chemotherapy nor immunotherapy in the way most people understand those terms. It is a targeted therapy, specifically an angiogenesis inhibitor, that works by cutting off a tumor’s blood supply rather than directly killing cancer cells or activating the immune system. That said, the classification gets a little blurry because Zirabev is technically an antibody, which places it in the broader biological therapy family that overlaps with some immunotherapy categories.
How Zirabev Works
Tumors need a blood supply to grow. To build one, many cancers produce large amounts of a protein called VEGF, which signals the body to form new blood vessels around the tumor. Zirabev is an antibody designed to latch onto VEGF molecules in the bloodstream and block them from reaching their receptors on blood vessel cells. Without that signal, the tumor can’t recruit new blood vessels, effectively starving it of oxygen and nutrients.
This mechanism is fundamentally different from what traditional chemotherapy does. Chemotherapy drugs are cytotoxic, meaning they kill rapidly dividing cells throughout the body, which is why they cause side effects like hair loss, nausea, and low blood counts. Zirabev doesn’t attack cells directly at all. It targets one specific protein involved in blood vessel growth, leaving most healthy cells alone. That’s why oncologists classify it as a targeted therapy rather than chemotherapy.
Why It’s Not Immunotherapy Either
When most people hear “immunotherapy,” they’re thinking of checkpoint inhibitors, the drugs that release the brakes on the immune system so it can recognize and destroy cancer cells. Zirabev doesn’t do that. It doesn’t activate T cells, block immune checkpoints, or train the immune system to find tumors.
The confusion arises because Zirabev is a monoclonal antibody, and antibodies are proteins the immune system naturally produces. Some cancer organizations categorize all monoclonal antibody therapies under a broad “immunotherapy” umbrella, which is technically accurate in a biological sense. The National Cancer Institute, however, classifies bevacizumab (the active drug in Zirabev) specifically as a targeted therapy and angiogenesis inhibitor. In practical terms, when your oncologist talks about immunotherapy, they mean something different from what Zirabev does.
Zirabev Is a Biosimilar to Avastin
Zirabev is a biosimilar version of Avastin (bevacizumab), which was one of the first angiogenesis inhibitors approved for cancer treatment. A biosimilar is essentially the generic equivalent of a biologic drug. The FDA approved Zirabev after confirming it works the same way, at the same effectiveness, with the same safety profile as the original Avastin. The main difference is cost: biosimilars are typically less expensive.
If you’ve read anything about Avastin and its uses, the same information applies to Zirabev. The two are interchangeable in terms of how they’re given, what cancers they treat, and what side effects they carry.
Cancers Zirabev Treats
Zirabev is approved for several cancer types, including metastatic colorectal cancer, certain types of non-small cell lung cancer, glioblastoma (an aggressive brain cancer), metastatic kidney cancer, and cervical cancer. In most of these cases, it is not used alone. It is given alongside chemotherapy drugs, where it complements their cell-killing action by simultaneously choking off the tumor’s blood supply.
This combination approach is important to understand. If you or someone you know is receiving Zirabev as part of a treatment plan, it’s very likely being paired with traditional chemotherapy agents. So while Zirabev itself isn’t chemotherapy, the overall regimen probably includes chemotherapy too.
How It’s Given
Zirabev is delivered as an intravenous infusion, similar to how many chemotherapy drugs are administered. You’ll sit in an infusion chair while the drug is delivered through an IV line. The first infusion typically takes about 90 minutes so the care team can monitor for reactions. If that goes well, later infusions can be shortened. The frequency depends on the specific cancer and treatment protocol, but infusions are commonly given every two or three weeks.
Side Effects to Expect
Because Zirabev targets blood vessel growth rather than killing cells indiscriminately, its side effect profile looks different from traditional chemotherapy. You’re unlikely to lose your hair from Zirabev alone, and severe nausea is less common than with cytotoxic drugs.
The side effects that are more characteristic of Zirabev relate to its effect on blood vessels and healing. High blood pressure is one of the most common issues. Nosebleeds, headaches, fatigue, and protein in the urine also occur frequently. Some people experience numbness or tingling in their hands and feet, loss of appetite, or diarrhea.
More serious but less common risks include gastrointestinal perforation, where a hole develops in the wall of the stomach or intestines. Warning signs include severe abdominal pain, fever, and vomiting. Because Zirabev affects blood vessel formation, it can also slow wound healing significantly. Surgeons typically want patients to stop the drug well before any planned procedure and wait before restarting it afterward. There is also an increased risk of blood clots and serious bleeding events. Some women who receive Zirabev may experience fertility effects.
When Zirabev is combined with chemotherapy, you’ll likely experience side effects from both treatments. The chemotherapy component may still cause hair loss, nausea, and drops in blood cell counts, even though Zirabev itself doesn’t.